RU2796402C1 - Catalytic composition for hydrogen production - Google Patents

Abstract

FIELD: hydrogen production.

SUBSTANCE: present invention relates to a catalyst composition for producing hydrogen gas containing nickel, at least one of the following promoters: Cu, Zn, and a carrier, represented by a steamed biochar or an equilibrium catalyst for liquid catalytic cracking of spent material. The proportion of nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.5 wt.% with respect to the carrier. In addition, the present invention relates to a method for producing a catalyst composition, a method for producing hydrogen gas, and a method for producing carbon nanotubes.

EFFECT: efficient conversion of methane into hydrogen.

13 cl, 1 tbl, 9 dwg, 2 ex

Description

FIELD OF TECHNOLOGY

[001] The present invention relates essentially to the production of fuels and, in particular, to the catalytic decomposition of methane.

BACKGROUND OF THE INVENTION

[002] The use of fossil fuels for energy production is one of the main factors contributing to excessive greenhouse gas emissions. When oil derivatives such as natural gas, gasoline and diesel are burned, huge amounts of carbon dioxide are released into the Earth's atmosphere, leading to alarming anthropogenic climate change, ocean acidification and global warming. According to the report of the International Energy Agency "World Energy Outlook 2012" (World energy outlook. IEA; 2012), by 2035, the world's energy demand will increase by more than a third. On the other hand, with the rapid decline of fossil fuels, the scientific community has faced the challenge of developing alternative fuels derived from sources other than oil in order to limit the dependence of energy production on oil.

[003] Recently, the focus has shifted towards hydrogen as an environmentally friendly fuel that produces only water in the process of obtaining energy. Hydrogen is the lightest and most accessible element in nature, which, unfortunately, is not present in its pure form and is therefore considered a secondary fuel. Hydrogen produced from other processes can easily be used to produce other clean hydrogen fuels such as hydrogen-enriched natural gas.

[004] Thus, hydrogen-enriched natural gas, commonly known as H-CNG, is a mixture of 10-30 v/v% hydrogen with 70-90 v/v% methane in compressed natural gas (CNG). This combination creates a balance between less flammable methane and more flammable hydrogen gas. Deviation of the proportion of hydrogen from 10-30 vol/vol.% leads to significant changes in fuel efficiency and emissions. Thus, the production of H-CNG requires mixing hydrogen and LNG in fixed ratios.

[005] Although LNG is readily available, hydrogen, which is a secondary fuel, has to be produced using various electrochemical, thermochemical, and photochemical technologies. One such technology widely used for the production of H-CNG is methane reforming. The process uses methane (the main component of natural gas) to produce hydrogen by partial conversion. Partial oxidation of methanol and methane are also well known processes for producing hydrogen. However, most of the processes currently in use inevitably produce some amounts of CO and CO ₂ , which are not only harmful to the environment, but also increase production costs by requiring the addition of costly separation steps.

[006] In connection with the above, the attention of researchers attracted the catalytic decomposition of methane as an alternative way to produce hydrogen without emitting greenhouse gases. The catalytic decomposition of methane has become one of the most promising methods due to the absence of the need to separate CO _x from hydrogen and the rather low cost of hydrogen production. However, this method requires the use of high performance catalytic materials capable of exhibiting catalytic activity for a long period of time without being destroyed during the process.

[007] A significant part of the effort has been directed to the development of catalysts devoid of the disadvantages inherent in the prior art. US8430937B2 discloses a series of catalysts comprising an MFI type zeolite, metal modified MFI type zeolites, and a heterogeneous solid acid catalyst, wherein the metal is Ga, Zn, In, Mo, W, Cr, Pt, Pd, Rh, Rm, Au, or Ir. . The catalyst is used to convert methane into combustible fuel.

[008] Despite the tremendous progress in catalytic methane decomposition processes in this field, the state of the art still needs a catalytic material that will not only provide efficient conversion of methane to hydrogen, but also be economically viable in terms of durability, efficiency and environmental friendliness. .

SUMMARY OF THE INVENTION

[009] In a first aspect of the present invention, a catalyst composition is provided comprising: (a) nickel; (b) at least one of the following promoters: Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd, Ag, Pt, or combinations thereof; and (c) a carrier, wherein the proportion of nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.2-5 wt.% relative to the carrier. [0010] In a second aspect of the present invention, there is provided a process for making a catalyst composition comprising: (a) nickel; (b) at least one of the following promoters: Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd, Ag, Pt, or combinations thereof; and (c) a carrier, wherein the proportion of nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.2-5 wt.% relative to the carrier, the process comprising the following steps: (a) contacting a nickel salt and a salt of at least one promoter to obtain a mixture; (b) impregnating the support material with the mixture to form an impregnated catalyst material; and (c) calcining the impregnated catalyst material to form a catalyst composition.

[0011] In a third aspect of the present invention, there is provided a process for producing hydrogen gas from a light hydrocarbon comprising the steps of: (a) adding a catalyst composition containing: (a) nickel; (b) at least one of the following promoters: Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd, Ag, Pt, or combinations thereof; and (c) a carrier material, wherein the proportion of nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.2-5 wt.% relative to the carrier in the reactor; (b) passing a light hydrocarbon over the catalyst bed at a temperature of 300-750 ⁰ C at atmospheric pressure for 20-50 hours; and (c) obtaining a product stream containing hydrogen gas.

[0012] In a fourth aspect of the present invention, a process for producing carbon nanotubes from a light hydrocarbon is provided, comprising the steps of: (a) adding a catalyst composition containing: (a) nickel; (b) at least one of the following promoters: Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd, Ag, Pt, or combinations thereof; and (c) a carrier, wherein the proportion of nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.2-5 wt.% relative to the carrier in the reactor; (b) passing a light hydrocarbon over the catalyst bed at a temperature in the range of 300-750 ⁰ C at atmospheric pressure for 20-50 hours; (c) obtaining a product stream containing hydrogen gas and a mixture; and (d) processing the mixture to produce carbon nanotubes.

[0013] In a fifth aspect of the present invention, the use of a catalyst composition containing: (a) nickel; (b) at least one of the following promoters: Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd, Ag, Pt, or combinations thereof; and (c) a carrier, wherein the proportion of nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.2-5 wt.% relative to the carrier to produce hydrogen gas and carbon nanotubes.

[0014] These and other features, aspects and advantages of the subject matter of the present invention are detailed in the following description and the appended claims. This summary is intended to provide a simplified introduction to a number of concepts. This summary is not intended to establish essential characteristics or essential features of the claimed subject matter, and is not intended to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The following drawings are part of the present description and further illustrate aspects of the present description of the invention. The description of the invention will be better understood by referring to the drawings in conjunction with a detailed description of certain embodiments disclosed herein.

[0016] FIG. 1 depicts a screening of an H-CNG catalyst for the H2 volume content of the evolved gas measured versus run time in minutes for MS105, MS106, MS107, MS108, MS109, MS110, MS111, MS112, and MS114 runs, in accordance with one embodiment. of the present invention.

[0017] FIG. 2 is a SEM image of a spent catalyst resulting from an MS024 run, in accordance with one embodiment of the present invention.

[0018] FIG. 3 depicts a thermogravimetric analysis curve for a spent catalyst resulting from an MS024 run, in accordance with one embodiment of the present invention.

[0019] FIG. 4(a) is a SEM image of a spent catalyst resulting from an MS105 run, in accordance with one embodiment of the present invention.

[0020] FIG. 4(b) depicts a thermogravimetric analysis curve for a spent catalyst resulting from an MS105 run, in accordance with one embodiment of the present invention.

[0021] In FIG. 5(a) depicts a thermogravimetric analysis curve for a spent catalyst resulting from an MS107 run, in accordance with one embodiment of the present invention.

[0022] FIG. 5(b) is an image of a spent catalyst resulting from a MS106 run under a scanning electron microscope, in accordance with one embodiment of the present invention.

[0023] FIG. 6(a) is a SEM image of a spent catalyst resulting from a MS108 run, in accordance with one embodiment of the present invention.

[0024] In FIG. 6(b) shows a Raman spectrum for multi-walled carbon nanotubes (MWNTs) obtained from an MS108 run, in accordance with one embodiment of the present invention.

[0025] In FIG. 6(c) depicts a thermogravimetric analysis curve for a spent catalyst resulting from an MS108 run, in accordance with one embodiment of the present invention.

[0026] FIG. 6(d) shows the results of energy dispersive x-ray analysis of a spent catalyst resulting from an MS108 run, in accordance with one embodiment of the present invention.

[0027] FIG. 7(a) is a SEM image of a spent catalyst resulting from a MS109 run, in accordance with one embodiment of the present invention.

[0028] In FIG. 7(b) shows a Raman spectrum for MWCNTs obtained from an MS109 run, in accordance with one embodiment of the present invention.

[0029] FIG. 7(c) depicts a thermogravimetric analysis curve for a spent catalyst resulting from an MS109 run, in accordance with one embodiment of the present invention.

[0030] FIG. 8(a) is a SEM image of a spent catalyst resulting from a MS114 run, in accordance with one embodiment of the present invention.

[0031] In FIG. 8(b) depicts a thermogravimetric analysis curve for a spent catalyst resulting from an MS114 run, in accordance with one embodiment of the present invention.

[0032] FIG. 8(c) shows the Raman spectrum for MWCNTs obtained from an MS114 run, in accordance with one embodiment of the present invention.

[0033] FIG. 9(a) depicts H-CNG fixed bed reactor catalyst screening by H ₂ volume content in the exhaust gas for a 5% Ni: 0.25% Cu: 0.25% Zn catalyst, in accordance with one embodiment. of the present invention.

[0034] FIG. 9(b) is an SEM image of a 5% Ni: 0.25% Cu: 0.25% Zn spent catalyst at 60 µm resolution, in accordance with one embodiment of the present invention.

[0035] FIG. 9(c) is a 100 nm SEM image of a spent catalyst containing 5% Ni: 0.25% Cu: 0.25% Zn, in accordance with one embodiment of the present invention.

DETAILED DISCLOSURE OF THE INVENTION

[0036] Specialists in this field will be obvious the possibility of changes and modifications of the present description of the invention, different from the described options. It should be understood that the present description of the invention includes all such changes and modifications. The disclosure also includes all such steps, features, compositions and compounds mentioned or referred to in this specification, either alone or together, as well as any and all combinations of any or more of such steps or features.

Definitions

[0037] For convenience, before further description of the present invention, some terms used in the description and examples will be given below. One of skill in the art should read in light of the rest of the disclosure and understand these definitions. The terms used in this document have generally accepted meanings known to those skilled in the art, however, for convenience and completeness, the terms and their meanings are given below.

[0038] A singular number is used to refer to one or more than one (ie, at least one) object.

[0039] The terms "comprise" and "comprising" are used in an all-encompassing open sense, meaning the possibility of adding additional elements. They should not be interpreted as "consists only of".

[0040] Throughout the description, unless the context otherwise requires, the word "comprise" and its variants, in particular "comprises" and "comprising", should be understood as implying the inclusion of the specified element or step or group of elements or steps, but not the exclusion of any another element or step or group of elements or steps.

[0041] The term "including" is used to mean "including, but not limited to". "Including" and "including but not limited to" are synonymous.

[0042] As used herein, the term "at least one" means one or more and thus includes both single components and mixtures/combinations.

[0043] As used herein, the term "rpm" refers to rotational speed/rpm. It is used to determine the rotational speed of any rotating part of the machine.

[0044] By "promoter" is meant a substance added to catalysts to improve their performance in a chemical reaction.

[0045] By "carbon nanotube" or "CNT" is meant a layer of covalently bonded carbon atoms rolled into a cylindrical structure. Single-walled carbon nanotubes contain a single layer of carbon atoms, while multi-walled carbon tubes contain two or more layers of carbon atoms rolled together.

[0046] By "carrier" is meant a substance having a large surface area and high stability and used as a catalyst base on which the catalyst is fixed. Such a support enhances the catalytic activity of the catalyst. An example is, in particular, a solid carrier such as nickel, silicates, charcoal, and the like.

[0047] By "ID/IG ratio" is meant the ratio of the intensity of the defect band (D) to the graphite band (G). This ratio helps to evaluate the quality of carbon nanotube structures.

[0048] By "effluent gas" is meant the liberated H-CNG or methane exiting the reactor during the methane conversion reaction. To analyze the effectiveness of the proposed catalytic composition, the volume content of H ₂ in the evolved gas is measured.

[0049] By "FCC" is meant a process called fluid catalytic cracking and carried out to regenerate spent catalyst material.

[0050] By "equilibrium catalyst" is meant an equilibrium zeolite material catalyst resulting from liquid catalytic cracking (FCC) of spent catalyst material. The term "equilibrium catalyst" as used herein can also mean "equilibrium waste material FCC catalyst".

[0051] The element symbols Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd, Ag, and Pt mean copper, zinc, molybdenum, cobalt, magnesium, cerium, titanium, zirconium, iron, palladium, silver and platinum, respectively. Accordingly, the symbols and element names are used as synonyms throughout the description.

[0052] The terms "LNG", "natural gas" and "methane" in this description are synonymous, since LNG is a form of natural gas stored under high pressure, and methane is the main component of both natural gas and LNG.

[0053] The terms "H-CNG" and "hydrogen-enriched natural gas" in this description are synonymous, as they correspond to a mixture of 10-30% hydrogen with natural gas.

[0054] " WE" means used sample, and "NWE" means unused sample, the numbers accompanying the abbreviations refer to the corresponding example number according to the corresponding table in the "Examples" section.

[0055] Ratios, concentrations, amounts, and other numerical data may be specified herein in range format. It should be understood that this range format is used for convenience and brevity only and is subject to flexible interpretation, i.e. to include not only the numeric values explicitly specified as the limits of the range, but also the individual numeric values or subranges included in the range as if each the numeric value and subrange have been explicitly specified. For example, a weight range of about 6-19% should be interpreted to include not only the explicitly stated limits of about 6% to about 19%, but also sub-ranges such as 7-18%, 9-12%, and so on, as well as individual amounts , including fractional amounts, within the specified ranges, for example, 6.5% and 6.225%.

[0056] As known in the art, H-CNG is the best alternative to compressed natural gas as a fuel in terms of low CO _x , NO _x , etc. emissions. H-CNG is considered to be an intermediate solution on the way to economical fuels based on H ₂ . The technology of catalytic decomposition of methane has opened up brilliant prospects in the field of hydrogen production. Because methane is a very stable molecule with four strong CH bonds, it is usually decomposed with a catalyst. The process of catalytic decomposition of methane contains a number of stages:

(a) methane adsorption on the catalyst surface

(b) breaking four C-H bonds and further separation of methane from the catalyst

(c) adsorption of hydrogen atoms on the catalyst surface and subsequent formation of an H ₂ molecule

[0057] The overall reaction can be expressed as follows, with carbon (C) being various forms of carbonaceous products that can be deposited alone or together with the spent catalyst. For partial conversion of methane, it is added in excess, and the degree of conversion is controlled by optimizing the composition of the catalyst, the reaction temperature, and other process parameters.

CH ₄ (ex.) → H ₂ + C + unreacted CH ₄

[0058] This method, in addition to the advantage of using catalytic materials for the decomposition of methane, also has certain disadvantages regarding the operation of the catalyst during the reaction. Problems such as rapid catalyst deactivation, costly regeneration of deactivated catalyst, and purification of carbon by-products produced during the reaction prevent most existing catalyst compositions from being successfully used commercially.

[0059] As mentioned above, catalyst deactivation is a topical issue. The deposition of carbon on the surface / in the pores of the active catalyst usually leads to its deactivation within a few hours after the start of the reaction and a decrease in the degree of methane conversion. In addition, the regeneration of the spent catalyst and the separation of precipitated carbonaceous products involves complex steps that increase the overall cost. On the other hand, the resulting carbon-containing material also requires subsequent purification, making it suitable for further use. According to the present invention, the above problems are solved by a catalyst composition that overcomes the disadvantages of the prior art by using hydrogen-rich natural gas as a fuel and MWCNTs with a purity of more than 90%.

[0060] The present invention provides a catalyst composition containing a small amount of nickel metal, steamed biochar or an equilibrium catalyst as a support, and a catalyst promoter. The catalyst composition according to the present invention, which has the additional advantage of a low amount of nickel metal in the range of 6-19 wt.%, also has a high catalytic activity and produces an evolved gaseous methane containing 10-30 vol.% hydrogen (H-CNG). The production of multi-walled carbon nanotubes (MWNTs) with a purity of 90-99% and an ID/IG ratio >1.0, along with H-CNG, makes this catalyst very economical to use. In addition to the benefits of using environmentally friendly biochar as a carrier, steam activation at 800 ^° C. creates a large number of reaction regions with high surface area and pore size. The spent catalyst formed during the reaction has a non-agglomerated form and is composed of high purity charcoal and carbon nanotubes (CNTs), which eliminates the problem of difficult separation of CNTs, facilitating separation due to their difference in thermal stability. Due to the excellent mechanical and electrical properties of high purity CNTs, the spent catalyst can also be used directly as a composite material. The present invention also proposes a process for the simultaneous production of H-CNG and high purity carbon nanotubes, essentially without greenhouse gas emissions of CO _x , NO _x . The process can be run over a long period of time (20-50 hours) and continuously produce H-CNG. Thus, the catalyst composition according to the present invention is a cost-effective alternative to conventional catalyst materials used in the catalytic decomposition of methane to produce hydrogen-based fuel.

[0061] Unless otherwise indicated, all technical and scientific terms used herein have the meaning commonly used by those skilled in the art to which this invention pertains. While any methods and materials similar or equivalent to those disclosed herein may be used in the practice or testing of the invention, preferred methods and materials will be described below. All publications cited herein are incorporated herein by reference.

[0062] The scope of the present invention is not limited to the specific embodiments disclosed herein for illustrative purposes only. Functionally equivalent products, compositions and methods are expressly included in the scope of this disclosure as described herein.

[0063] In one embodiment, the present invention provides a catalyst composition comprising: (a) nickel; (b) at least one of the following promoters: Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd, Ag, Pt, or combinations thereof; and (c) a carrier, wherein the proportion of nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.2-5 wt.% relative to the carrier. In one embodiment, the present invention provides a catalyst composition disclosed herein, in which the proportion of nickel is 8-15 wt.% in relation to the carrier, and the proportion of at least one promoter is 0.3-3 wt.% in relation to the carrier. In another embodiment of the present invention, the proportion of nickel is 9-11 wt.%, and the proportion of at least one promoter is 0.5-1 wt.% relative to the carrier.

[0064] In one embodiment, the present invention provides a catalyst composition comprising: (a) nickel; (b) at least one promoter in the form of a combination of Cu and Zn; and (c) a carrier, wherein the proportion of nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.2-5 wt.% relative to the carrier.

[0065] In one embodiment, the present invention provides a catalyst composition comprising: (a) nickel; (b) at least one promoter in the form of a combination of Cu and Zn; and (c) a carrier, wherein the proportion of nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.2-5 wt.% with respect to the carrier, and the proportion of Cu is 0.3-4 wt. . %, and the proportion of Zn is 0.3-4 wt. % relative to the carrier. In another embodiment of the present invention, the proportion of Cu is 0.4-3 wt.%, and the proportion of Zn is 0.4-3 wt.% relative to the carrier. In another embodiment of the present invention, the proportion of Cu is 0.5-2 wt.%, and the proportion of Zn is 0.5-2 wt.% relative to the carrier.

[0066] In one embodiment, the present invention provides a catalyst composition comprising: (a) nickel; (b) at least one of the following promoters: Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd, Ag, Pt, or combinations thereof; and (c) a carrier, wherein the proportion of nickel is 6-19 wt.%, the proportion of at least one promoter is 0.2-5 wt.% relative to the carrier, and the carrier is a steamed biochar or an equilibrium catalyst. In one of the embodiments of the present invention proposed a catalyst composition containing: (a) Nickel; (b) at least one of the following promoters: Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd, Ag, Pt, or combinations thereof; and (c) steamed biochar as a carrier with a surface area of 700-950 m ² /g and a pore volume of 0.60-0.70 cc. cm/g, and the proportion of Nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.2-5 wt.% with respect to the media.

[0067] In one embodiment, the present invention provides a catalyst composition comprising: (a) nickel; (b) at least one of the following promoters: Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd, Ag, Pt, or combinations thereof; and (c) steamed biochar as a carrier obtained by heating the feedstock, which is sawdust, rice straw, rice husk, sugar cane pomace, other agricultural waste, or combinations thereof, with the proportion of nickel being 6-19 wt.%, and the proportion , at least one promoter is 0.2-5 wt.% in relation to the media.

[0068] In one embodiment, the present invention provides a catalyst composition comprising: (a) nickel; (b) at least one of the following promoters: Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd, Ag, Pt, or combinations thereof; and (c) steamed biochar as a carrier obtained by heating a feedstock that is sawdust, rice straw, rice husks, sugar cane pomace, other agricultural waste, or combinations thereof, at a temperature of 700-900°C for 5-10 hours , and the proportion of Nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.2-5 wt.% with respect to the media. In another embodiment of the present invention, steamed biochar as a carrier was obtained by heating the feedstock at a temperature of 750-850°C for 7-9 hours.

[0069] In one embodiment, the present invention provides a catalyst composition comprising: (a) nickel; (b) at least one of the following promoters: Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd, Ag, Pt, or combinations thereof; and (c) steamed biochar as a carrier with a surface area of 700-950 m ² /g and a pore volume of 0.60-0.70 cc. cm / g, obtained by heating the feedstock, which is sawdust, rice straw, rice husk or sugar cane pomace, with the proportion of nickel being 6-19 wt.%, and the proportion of at least one promoter is 0.2-5 wt.% in relation to the media.

[0070] In one embodiment, the present invention provides a catalyst composition comprising: (a) nickel; (b) at least one promoter in the form of a combination of Cu and Zn; and (c) steamed biochar as a carrier with a surface area of 700-950 m ² /g and a pore volume of 0.60-0.70 cc. cm/g, and the proportion of nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.2-5 wt.% with respect to the media.

[0071] In one embodiment, the present invention provides a catalyst composition comprising: (a) nickel; (b) at least one promoter in the form of a combination of Cu and Zn; and (c) steamed biochar as a carrier with a surface area of 700-950 m ² /g and a pore volume of 0.60-0.70 cc. cm/g, and the proportion of Nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.2-5 wt.% with respect to the carrier, and the proportion of Cu is 0.4-4 wt. %, and the proportion of Zn is 0.4-4 wt. % relative to the carrier.

[0072] In one embodiment, the present invention provides a catalyst composition comprising: (a) nickel; (b) at least one promoter in the form of a combination of Cu and Zn; and (c) steamed biochar as a carrier with a surface area of 700-950 m ² /g and a pore volume of 0.60-0.70 cc. cm / g, obtained by heating the feedstock, which is sawdust, rice straw, rice husk, sugar cane pomace, other agricultural waste, or combinations thereof, with the proportion of nickel being 6-19 wt.%, and the proportion of at least one the promoter is 0.2-5 wt.% relative to the carrier.

[0073] In one embodiment, the present invention provides a catalyst composition comprising: (a) nickel; (b) at least one promoter in the form of a combination of Cu and Zn, and the proportion of Cu is 0.4-4 wt. %, and the proportion of Zn is 0.4-4 wt. % relative to the carrier; and (c) steamed biochar as a carrier with a surface area of 700-950 m ² /g and a pore volume of 0.60-0.70 cc. cm / g, obtained by heating the feedstock, which is sawdust, rice straw, rice husk, sugar cane pomace, other agricultural waste, or combinations thereof, and the proportion of Nickel is 6-19 wt.%.

[0074] In one embodiment, the present invention provides a method for making the catalyst composition disclosed herein, the method comprising the steps of: (a) contacting a nickel salt and a salt of at least one promoter to form a mixture; (b) impregnating the carrier with the mixture to form an impregnated catalyst material; and (c) calcining the impregnated catalyst material to form a catalyst composition.

[0075] In one embodiment, the present invention provides a method for making the catalyst composition disclosed herein, wherein at least one promoter is Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd , Ag, Pt or a combination thereof.

[0076] In one embodiment, the present disclosure provides a method for making the catalyst composition disclosed herein, the method comprising the steps of: (a) contacting a nickel salt and a salt of at least one promoter at a temperature of 30-35 ^° C for 40-120 minutes to obtain a mixture; (b) impregnating the carrier with the mixture at a temperature of 30-35 ^° C. for 40-120 minutes to obtain an impregnated catalyst material; (c) calcining the impregnated catalyst material in an inert atmosphere at 530-570 ^° C. for 250-350 minutes to obtain a catalyst composition.

[0077] In one embodiment, the present invention provides a method for making the catalyst composition disclosed herein, the method comprising the steps of: (a) contacting a nickel salt and a salt of at least one promoter to form a mixture; (b) impregnating the carrier with the mixture to form an impregnated catalyst material; and (c) calcining the impregnated catalyst material to form a catalyst composition, wherein the carrier is steamed biochar obtained by steaming a feedstock of sawdust, rice straw, rice husks, sugar cane pomace, other agricultural waste, and combinations thereof at a temperature of 700- 900°C for 5-10 hours.

[0078] In one embodiment, the present invention provides a method for making the catalyst composition disclosed herein, the method comprising the steps of: (a) contacting a nickel salt and a salt of at least one promoter to form a mixture; (b) impregnating the carrier with the mixture to form an impregnated catalyst; (c) drying the impregnated catalyst material to obtain a dried catalyst; and (d) calcining the dried catalyst to obtain a catalyst composition.

[0079] In one embodiment, the present disclosure provides a method for making the catalyst composition disclosed herein, the method comprising the steps of: (a) contacting a nickel salt and a salt of at least one promoter at a temperature of 30-35 ^° C for 40-120 minutes to obtain a mixture; (b) impregnating the carrier with the mixture at a temperature of 30-35 ^° C. for 40-120 minutes to obtain an impregnated catalyst material; (c) drying the impregnated catalyst material at 90-120 ^° C. for 47-50 hours to obtain a dried catalyst; and (d) calcining the dried catalyst in an inert atmosphere at a temperature of 530-570 ^o C for 250-350 minutes to obtain a catalyst composition.

[0080] In one embodiment, the present invention provides a process for making the catalyst composition disclosed herein, wherein the nickel salt is nickel nitrate, nickel sulfate, nickel phosphate, nickel carbonate, nickel bicarbonate, nickel halide, nickel hydroxide, nickel sulfide, nickel carbide, nickel nitride, nickel oxide, nickel carboxylate, or a mixture thereof.

[0081] In one embodiment, the present invention provides a process for making the catalyst composition disclosed herein, wherein the salt of at least one promoter is a nitrate, sulfate, phosphate, carbonate, bicarbonate, halide, hydroxide, sulfide, carbide , nitride, oxide, carboxylate, or a mixture thereof, and in which at least one promoter is Cu, Zn, Mo, Co, Mg, Ce, Ti, Zr, Fe, Pd, Ag, Pt, or a combination thereof.

[0082] In one embodiment, the present invention provides a process for making the catalyst composition disclosed herein, wherein the salt of at least one promoter is a nitrate, sulfate, phosphate, carbonate, bicarbonate, halide, hydroxide, sulfide, carbide , nitride, oxide, carboxylate, or a mixture thereof, and in which at least one promoter is Cu, Zn, or a combination thereof. In another embodiment of the present invention, the salt of at least one promoter is a nitrate and at least one promoter is a combination of Cu and Zn.

[0083] In one embodiment, the present invention provides a process for producing hydrogen gas from a light hydrocarbon comprising the steps of: (a) adding the catalyst composition disclosed herein to a reactor; (b) passing a light hydrocarbon over the catalyst bed at a temperature of 300-750°C and atmospheric pressure for 20-50 hours; and (c) obtaining a product stream containing gaseous hydrogen, and the catalyst composition contains steamed biochar or equilibrium catalyst as a carrier. In another embodiment of the present invention, the passage of a light hydrocarbon over the catalyst bed is carried out at a temperature of 400-700°C and atmospheric pressure for 20-50 hours. In another embodiment of the present invention, the passage of light hydrocarbon over the catalyst bed is carried out at a temperature of 500-600°C and atmospheric pressure for 20-50 hours. In another embodiment of the present invention, the passage of a light hydrocarbon over the catalyst bed is carried out at a temperature of 400-600°C and atmospheric pressure for 21-46 hours.

[0084] In one embodiment, the present invention provides a process for producing hydrogen gas from a light hydrocarbon disclosed herein, wherein the product stream is substantially free of carbon monoxide and carbon dioxide.

[0085] In one embodiment, the present invention provides a process for producing hydrogen gas from a light hydrocarbon disclosed herein, wherein the product stream is free of carbon monoxide and carbon dioxide.

[0086] In one embodiment, the present invention provides a process for producing hydrogen gas from a light hydrocarbon comprising the steps of: (a) adding the catalyst composition disclosed herein to a reactor; (b) passing a light hydrocarbon over the catalyst bed at a temperature of 300-750°C and atmospheric pressure for 20-50 hours; and (c) obtaining a product stream containing gaseous hydrogen, wherein the process produces hydrogen gas in an amount of 10-30% of the total light hydrocarbon content.

[0087] In one embodiment, the present invention provides a process for producing hydrogen gas from a light hydrocarbon comprising the steps of: (a) adding the catalyst composition disclosed herein to a reactor; (b) passing a light hydrocarbon over the catalyst bed at a temperature of 300-750°C and atmospheric pressure for 20-50 hours; and (c) obtaining a product stream containing hydrogen gas, and the product stream is processed to obtain carbon nanotubes, and the catalyst composition contains steamed biochar or equilibrium catalyst as a support.

[0088] In one embodiment, the present invention provides a process for producing hydrogen gas from a light hydrocarbon comprising the steps of: (a) adding the catalyst composition disclosed herein to a reactor; (b) passing a light hydrocarbon over the catalyst bed at a temperature of 300-750°C and atmospheric pressure for 20-50 hours; and (c) obtaining a product stream containing hydrogen gas, the process producing hydrogen gas in an amount of 10-30% of the total light hydrocarbon content, the product stream being treated to produce carbon nanotubes.

[0089] In one embodiment, the present invention provides a process for producing hydrogen gas from a light hydrocarbon to produce a product stream containing hydrogen gas, wherein the product stream is treated to produce multi-walled carbon nanotubes with an ID/IG ratio of 0.5-2.5.

[0090] In one embodiment, the present invention provides a process for producing hydrogen gas from a light hydrocarbon comprising the steps of: (a) adding the catalyst composition disclosed herein to a reactor; (b) passing a light hydrocarbon over the catalyst bed at a temperature of 300-750°C and atmospheric pressure for 20-50 hours; (c) obtaining a product stream containing hydrogen gas and a mixture; and (d) processing the mixture to produce carbon nanotubes. In another embodiment of the present invention, the passage of a light hydrocarbon over the catalyst bed is carried out at a temperature of 400-700°C and atmospheric pressure for 21-48 hours. In another embodiment of the present invention, the passage of a light hydrocarbon over the catalyst bed is carried out at a temperature of 500-600°C and atmospheric pressure for 22-46 hours.

[0091] In one embodiment, the present invention provides a process for producing carbon nanotubes from a light hydrocarbon disclosed herein, wherein the product stream is substantially free of carbon monoxide and carbon dioxide.

[0092] In one embodiment, the present invention provides a process for producing hydrogen gas from a light hydrocarbon disclosed herein, wherein the light hydrocarbon is not limited to an aliphatic hydrocarbon, but may also be an aromatic and/or alicyclic hydrocarbon, provided that the hydrocarbons are decomposable with the formation of hydrogen. Aliphatic hydrocarbons may have from 1 to 20 carbon atoms, more preferably from 1 to 12 carbon atoms, and be in particular decane, nonane, heptane, pentane, isopentane, or petroleum fractions such as naphtha and liquefied petroleum gas (LPG) . Aromatic hydrocarbons may have from 5 to 16 carbon atoms and be, in particular, benzene, tetralin, ethylbenzene, xylene or toluene. Alicyclic hydrocarbons may have from 3 to 12 carbon atoms and be in particular cyclopentane, cyclobutene, cyclopropane, cycloheptane or ethylcyclopentane.

[0093] In one embodiment, the present invention provides a process for producing carbon nanotubes from a light hydrocarbon disclosed herein, wherein the purity of the carbon nanotubes is 90-99%.

[0094] In one embodiment, the present invention provides a process for simultaneously producing carbon nanotubes and hydrogen gas from a light hydrocarbon disclosed herein, wherein the light hydrocarbon is methane, ethane, propane, butane, ethylene, acetylene, or combinations thereof.

[0095] In one embodiment, the present invention provides a process for simultaneously producing carbon nanotubes and hydrogen gas from a light hydrocarbon disclosed herein, wherein the product stream is free of carbon monoxide and carbon dioxide.

[0096] In one embodiment, the present invention provides a method for simultaneously producing carbon nanotubes and hydrogen gas from a light hydrocarbon disclosed herein, wherein the product stream is substantially free of carbon monoxide and carbon dioxide.

[0097] In one embodiment, the present invention provides a process for producing carbon nanotubes from a light hydrocarbon disclosed herein, wherein the light hydrocarbon is methane, ethane, propane, butane, ethylene, acetylene, or combinations thereof.

[0098] In one embodiment, the present invention provides a process for producing hydrogen gas from a light hydrocarbon disclosed herein, wherein the light hydrocarbon is methane, ethane, propane, butane, ethylene, acetylene, or combinations thereof.

[0099] In one embodiment, the present invention provides a process for producing carbon nanotubes from a light hydrocarbon disclosed herein, wherein the reactor is a fluidized bed reactor, a moving bed reactor, a fixed bed reactor, or a rotating bed reactor. In another embodiment of the present invention, the reactor is a fluidized bed reactor.

[00100] In one embodiment, the present invention provides a process for producing hydrogen gas from a light hydrocarbon disclosed herein, wherein the reactor is a fluidized bed reactor, a moving bed reactor, a fixed bed reactor, or a rotating bed reactor. In another embodiment of the present invention, the reactor is a fluidized bed reactor.

[00101] In one embodiment, the present invention provides a process for producing carbon nanotubes from a light hydrocarbon, comprising the steps of: (a) adding the catalyst composition disclosed herein to a reactor; (b) passing a light hydrocarbon over the catalyst bed at a temperature of 300-750°C and atmospheric pressure for 20-50 hours; (c) obtaining a product stream containing gaseous hydrogen and a mixture; and (d) treating the mixture to produce carbon nanotubes by one of the following methods: acid treatment, washing, drying, or combinations thereof.

[00102] In one embodiment, the present invention provides a process for producing carbon nanotubes from a light hydrocarbon, comprising the steps of: (a) adding the catalyst composition disclosed herein to a reactor; (b) passing a light hydrocarbon over the catalyst bed at a temperature of 300-750°C and atmospheric pressure for 20-50 hours; (c) obtaining a product stream containing hydrogen gas and a mixture; and (d) processing the mixture to produce carbon nanotubes, wherein the carbon nanotubes are multi-walled carbon nanotubes with an ID/IG ratio of 0.5 to 2.5. In another embodiment of the present invention, the carbon nanotubes are multi-walled carbon nanotubes with an ID/IG ratio of 0.7 to 2.5. In another embodiment of the present invention, the carbon nanotubes are multi-walled carbon nanotubes with an ID/IG ratio of 1.0 to 2.5.

[00103] In one embodiment, the present invention provides for the use of the catalyst composition disclosed herein to produce hydrogen gas and carbon nanotubes.

[00104] In one of the embodiments of the present invention, the catalyst composition can be slightly modified to obtain various forms of carbon-containing products that can be deposited separately or together with the spent catalyst, and the carbon-containing product can be SWCNTs, MWCNTs, carbon nano-onions, carbon nano-rings, graphitic carbon, amorphous carbon, or combinations thereof.

[00105] While the subject matter has been described in sufficient detail with reference to certain examples and embodiments, other embodiments are possible.

EXAMPLES

[00106] Below, the disclosure will be illustrated by the examples used, intended to illustrate the operation of the invention and are not intended to limit the scope of the present invention. Unless otherwise indicated, all technical and scientific terms used herein have the meaning commonly used by those skilled in the art to which this invention pertains. Although methods and materials similar or equivalent to those described herein may be used in the practice of the disclosed methods and compositions, examples of methods, devices and materials are provided herein. It should be understood that the present invention is not limited to the described methods and experimental conditions, provided that such methods and conditions are applicable.

[00107] The used and unused samples disclosed in the following sections highlight the criticality of the working percentages of the various components, i.e. nickel, promoter and carrier, to obtain a catalyst composition according to the present invention. In addition, the critical importance of the presence of all components to achieve the desired catalytic activity is indicated. The absence of any of the above components or their replacement with any other component significantly affects the catalytic activity, the required percentage of H ₂ in the evolved gas, and the purity of carbon nanotubes obtained from it.

Materials and methods

[00108] Biochar was obtained by rapid pyrolysis of sawdust in the reactor of the pilot plant. An equilibrium FCC catalyst was purchased from the market. Equipment for scanning electron microscopy and energy dispersive X-ray analysis was purchased from Jeol, Korea. Equipment for thermogravimetric analysis was purchased from TA instruments, USA. The Raman analyzer was purchased from Rinissaw, UK. The fixed bed reactor was developed by the R&D department of HPCL.

EXAMPLE 1

Catalyst fabrication and characteristics

[00109] A series of experiments were conducted to evaluate the effect of various variables, including metal fraction, carrier, and catalyst consumption, on overall catalyst performance in terms of H ₂ volume content produced as effluent gas and carbon nanotube purity produced simultaneously. For this, various catalysts were synthesized, the composition of which is shown in Table 1, and then subjected to a fluidized bed reactor system to produce hydrogen by converting methane (natural gas).

Example 1.1: Manufacture of a Catalyst Composition

[00110] The nickel metal catalyst was made by wet impregnation. Ni(NO ₃ ) ₂ ⋅6H ₂ O, Cu(NO ₃ ) ₂ ⋅3H ₂ O, and Zn(NO ₃ ) ₂ ⋅6H ₂ O were used as metal precursor salts to introduce nickel, copper, and zinc into the solution. The measured amounts of Cu(NO ₃ ) ₂ ⋅3H ₂ O and Zn(NO ₃ ) ₂ ⋅6H ₂ O (calculated from the final mass content of the metal in the finished catalyst) were mixed with demineralized water. The required amount of Ni(NO ₃ ) ₂ ⋅6H ₂ O was added to distilled water in a 500 ml conical flask and heated to a temperature of about 30°C, which was maintained for 1 hour with continuous stirring to obtain a mixture. On the other hand, activated biochar was made by steaming biochar at 800°C for 8 hours. The resulting steamed biochar had a BET surface area of 860 m ² /g with a large pore volume of 0.66 cc/g, while the pre-boiled biochar had negligible surface area and porosity. After that, a measured amount of steamed biochar was added to the same conical flask for impregnation of the catalyst, and the resulting solution was stirred for 1 hour at a temperature of about 30°C. The mixed solution was then transferred to a 1000 ml round bottom flask and stirred again at 70-80 rpm in a rotary steamer to remove water from the product. Next, the impregnated catalyst material was dried in an oven at 110°C for 48 hours, calcined at 550°C in an inert atmosphere for 5 hours to obtain a finished catalyst, which was subsequently crushed and sieved to obtain fluidized particles in the range of 45 to 150 microns.

Example 1.2: Process for the production of hydrogen-enriched natural gas

[00111] In the first step, the catalyst was placed in a hopper, from where 15 g of the catalyst was transferred to a fluidized bed reactor. In preparation for the reaction, the reactor was heated to 550 ^o C and purged with gaseous N ₂ with a flow rate of 15 st.l/hour (standard liters per hour). Then the loaded catalyst was reduced/activated in an atmosphere of hydrogen-rich natural gas/pure hydrogen at a temperature of 550-580°C for 3-5 hours. Thereafter, the flow controlled network natural gas (feed gas) was passed through the catalyst bed in the fixed bed reactor, and the reaction proceeded for more than 20 hours at a temperature of 550°C. Hydrogen gas was produced by a catalytic reaction with natural gas, leaving hydrogen-enriched natural gas (H-CNG) as a product stream and a spent catalyst consisting of charcoal and carbon nanotubes. Another by-product of the reaction was MWCNTs, which, being heavier, settled to the bottom of the reactor. The H-CNG product stream was passed through a cyclone/high temperature filter and collected for further use, and the heat obtained from the high temperature filter was used to activate the catalyst. After completion of the reaction in the fixed bed reactor, the spent catalyst was removed by vacuum or high speed treatment to a spent catalyst discharge vessel. This spent catalyst was also analyzed by thermogravimetric analysis, scanning electron microscopy and Raman analysis. At various time intervals, a sample of the resulting gas was taken and analyzed on a gas chromatograph with a flame ionization detector and a thermal conductivity detector. The differential pressure sensor was constantly monitored to stop the reaction when the deposition of CNTs on the catalyst resulted in a significant pressure drop. This further leads to jamming of the gas distributor. Therefore, although the catalyst may have been active in some cases, the reaction was terminated due to a significant pressure drop. In commercial type reactors, this phenomenon can be avoided by using ring diffuser gas distributors instead of laboratory sintered or mesh distributors.

Example 1.3: Catalyst Composition

[00112] Developed a set of catalysts with different proportions of nickel and support. For runs MS-105 and MS-106, although the reduction temperature varied between 550-580 ^° C., the reaction was carried out at 550° C. for 5 hours. For runs MS107-MS114, reduction was carried out at a temperature of 580 ^o C for 6 hours, and the reaction at 550°C. The volume content of H ₂ in the evolved gas H-CNG was constantly recorded depending on the duration of the reaction (hours). The mass of the collected spent catalyst and the % purity of the carbon in the carbon nanotubes deposited thereon were also measured. Table 1 shows the maximum and minimum values of the obtained volume content of H ₂ in the evolved gases when using catalysts with different weight content of nickel, copper and zinc. The catalyst carrier was steamed biochar with alumina (Al ₂ O ₃ ), activated carbon, and an equilibrium catalyst. While most of the catalysts were loaded at an hourly gas space velocity of 2 l/g/h, MS106 was loaded at an hourly gas space velocity of 1.66 l/g/h. The density of the fresh alumina catalyst was 888 kg/m ³ and the density of the spent catalyst was 389.8 kg/m ³ . The density of the fresh catalyst with steamed biochar was 250-350 kg/m ³ and the density of the spent catalyst was 150-250 kg/m ³ . As the reaction proceeded, the density of the particles decreased, as a result of which they became denser and led to the termination of the fluidization of the bed. Experiments with MS105-108 were terminated after several hours of methane supply. To restart the experiment, a hydrogen purge was carried out for 1 hour, as the reactor was cooled in an N ₂ environment overnight. Therefore, in FIG. 1, fluctuations in the content of H ₂ in the evolved gases are observed. Starting from MS109 and further up to MS114, the experiments were carried out in a round-the-clock mode of operation of the setup without days off. This made it possible to achieve a stable conversion.

[00113] The MS024 run was a control experiment using only steamed biochar without any metal impregnation. The reaction was carried out in a fixed bed reactor for 3 hours. Natural gas was supplied through the pipeline at a flow rate of 10 tablespoons/hour, and the reaction temperature for producing hydrogen was set to 750°C. The resulting spent steamed biochar from the control experiment was subjected to scanning electron microscopy. In FIG. 2 shows that the carbon from the steamed biochar base has an essentially porous structure with a minimal amount of carbon nanotubes (40-100 nm in diameter). In addition, the thermogravimetric analysis data in FIG. 3, which were affected by carbon from steamed biochar, showed low temperature degradation at temperatures below 450 ^o C, while the thermogravimetric analysis images for other runs showed high thermal stability of CNTs at temperatures up to 550 ^o C. In addition, the run produced > 30 vol.% H ₂ and produced >5% greenhouse gases CO and CO ₂ , which is completely undesirable. Thus, the obtained results substantiated the inconsistency of using only steamed biochar for the production of H-CNG.

[00114] MS110 was a control experiment without any metal impregnation on commercially available activated carbon that initially showed 12 vol% H ₂ in the outgassing and dropped to 2.5 vol% H ₂ over the next 5 hours. Due to the absence of metal, in particular aluminum in the form of Al ₂ O ₃ , the activated carbon base remained 98% pure. However, the amount of spent catalyst collected was very small compared to another catalyst charged in the same amount of 15 g.

[00115] Run MS107 (20% Ni, 1.6% Cu, 1.6% Zn, unused sample) was performed for 15 hours based on Al ₂ O ₃ . Although this run showed 10-30 vol.% H ₂ in the evolved gases, the reaction could not continue after 15 hours due to agglomeration of the spent catalyst. In addition, when Al ₂ O ₃ was added, the spent catalyst had a carbon purity of only 70%, as shown in the thermogravimetric analysis curve in FIG. 5(a).

[00116] The MS106 run (10% Ni, 0.5% Cu, 0.5% Zn, unused sample) was run on Al ₂ O ₃ for 18 hours, after which, although it was possible to collect more spent catalyst than in the run MS105, however, the amount of H ₂ in the evolved gases was <10 vol.%. The image of the collected spent catalyst with a diameter of 94.1 nm under a scanning electron microscope is shown in FIG. 5(b). The purity of the CNTs in the spent catalyst was 75%. Since Al ₂ O ₃ as a catalyst support did not show the desired results, further tests were carried out with steamed biochar and activated carbon as carriers.

[00117] An MS105 run (20% Ni, 1.6% Cu, 1.6% Zn, unused sample) performed on steamed biochar showed >30 vol% H ₂ in the off gases. The run was performed for 15 hours. 20.51 g of spent catalyst was collected, less compared to other catalyst formulations. The image under the scanning electron microscope in Fig. 4(a) shows the formation of carbon nanotubes with a diameter of 30-70 nm. Thermogravimetric analysis (FIG. 4(b)) of the obtained CNTs showed a purity of 85%, well below the desired range. Since both MS107 and MS105 catalysts with 20% Ni, regardless of the catalyst support, showed negative results in terms of H ₂ volume content, further operation of the catalyst was tested with a lower nickel percentage.

[00118] An MS108 (10% Ni, 0.5% Cu, 0.5% Zn, sample used) run on a steamed biochar base for 18 hours met the requirement for a hydrogen volume content of 10-30 vol.%, i.e. the recorded range was 18.4-26.9%. Upon completion of the reaction, a significant amount of spent catalyst (49 g) was recovered. In FIG. 6(a) shows SEM images of the spent catalyst showing completed formation of 28.2 nm diameter carbon nanotubes. In addition, the purity of CNTs and MWCNTs was also examined by thermogravimetric analysis and Raman spectrometry, respectively. According to the results of thermogravimetric analysis, as shown in Figure 6(c), the purity of CNTs was 96%. The Raman studies in Fig. 6(a) for MWCNTs showed that the ID/IG ratio is greater than 2.0, i. e. equals 2.14. The energy dispersive X-ray analysis results shown in FIG. 6(d) further confirmed the formation of the catalyst in the appropriate stoichiometry.

[00119] A run of MS109 (10% Ni, 0.5% Cu, 0.5% Zn, sample used) continuously performed for 14 hours showed only a slight decrease in the amount of spent catalyst collected. However, the H ₂ content was in the required range of 10-30% by volume, and thermogravimetric analysis showed a purity of 95% CNTs (FIG. 7(c)). Reducing the run time from 18 hours for MS108 to 14 hours for MS109 results in a decrease in the ID/IG ratio of MWCNTs from 2.14 to 2.04, respectively, as shown in the Raman spectrum in FIG. 7(b). In FIG. 7(a) further shows the completed formation of carbon nanotubes with a diameter of approximately 33 nm.

[00120] An MS111 run (10% Ni, 0.5% Cu, 0.5% Zn, unused sample) was performed to test the effectiveness of a 10% Ni fraction on a carrier other than steamed biochar. Therefore, in this case, activated carbon impregnated with a 10% nickel catalyst for 8 hours was used. Surprisingly, the run showed a very low volume content of H ₂ in the evolved gases, ie. from 2 to 3.5%. Even with 15 g of catalyst, the amount of spent catalyst remained very low (11 g) and the resulting CNTs also had a purity of only 82.5%. Thus, activated carbon has been found to be an unsuitable carrier for the catalyst composition of the present invention. With the exception of MS110 and MS111, carbon nanotubes 30-100 nm in diameter are present in the rest of the spent catalyst.

[00121] Further studies on the catalyst containing 10% nickel were carried out using an equilibrium FCC catalyst as a catalyst support. The equilibrium catalyst is one of the cost-effective and available waste carriers. As a control experiment, MS112 (unused sample) was run using an equilibrium catalyst without metal impregnation, which showed almost zero methane conversion even with a loading of 15 g of catalyst.

[00122] An MS114 run (10% Ni, 0.5% Cu, 0.5% Zn, equilibrium catalyst as base, sample used) was performed continuously for 45 hours. It made it possible to obtain a stable volume content of hydrogen in the evolved gas (from 23.9 to 21.8 vol.%) during the entire operation time, without causing the termination of fluidization or agglomeration of the catalyst. The spent catalyst was significantly reduced (>100 g) and the resulting CNTs were 93% pure as shown in the thermogravimetric analysis curve in FIG. 8(b). In FIG. 8(a) shows an image of a spent catalyst with carbon nanotube formation under a scanning electron microscope, and FIG. 8(c) is a Raman spectrum showing an ID/IG ratio of 1.83 for the resulting MWCNTs.

[00123] In general, based on the above experimental analysis, it was concluded that the catalyst composition with 10% nickel, 0.5% Cu and 0.5% Zn on a carrier in the form of steamed biochar was the most effective in obtaining H-CNG with H ₂ enrichment in the required range of 10-30% over an extended period of 45 hours. Image of the collected spent catalyst of this composition under a scanning electron microscope showed the complete formation of carbon nanotubes with a purity above 95%. In addition, MWCNTs obtained in the course of the reaction were characterized by a smaller number of structural defects, demonstrating an ID/IG ratio >2.0, which allows them to be successfully used in various fields of optics, electronics, construction, and biomedicine. In addition, the present catalyst composition showed no significant emission of carbon dioxide and greenhouse gases during the entire reaction time.

EXAMPLE 2

Impact of nickel reduction

[00124] To study the effect of a reduced proportion of nickel in the catalyst composition, a catalyst composition was developed containing 5% nickel, 0.25% copper and 0.25% zinc (5:0.25:0.25) based on steamed biochar . The catalyst was reduced at 550° C. for 5 hours and fed into the fixed bed reactor system. Methane gas (CNG) was used as the source gas for performing the conversion. Data on the volume content of H ₂ in the evolved gases are shown in FIG. 9(a), which show no more than 3.7 vol.% H ₂ , which is undesirably low and impractical for such energy intensive reaction systems. In addition, the SEM image of the spent catalyst shown in FIG. 9(b) with a resolution of 60 µm and in FIG. 9(c) at a higher resolution of 100 nm showed only slight carbon nanotube nucleation without pronounced carbon nanotube formation. Thus, from the above analysis, it can be concluded that a reduced fraction of nickel at a level of 5% does not provide the necessary hydrogen production, and also makes the spent catalyst unsuitable for further reduction of carbon nanotubes.

Advantages of the present invention

[00125] The above embodiments disclosed herein and their equivalents have many advantages, including those described.

[00126] The present invention discloses a catalyst composition containing a low amount of nickel metal in the range of 6-19 wt.% based on steam-activated biochar. The catalyst shows excellent results in the production of hydrogen and ensures the enrichment of natural gas with hydrogen at the level of 10-30%. Thus, the H-CNG fuel obtained from it can be successfully used in various industries using high-energy processes. In the present disclosure, steam-activated biochar, which is readily available in the environment and biodegradable, is used as the catalyst carrier. This eliminates the need for other heavy metal bases and significantly reduces the generation of chemical waste. In addition, the present catalyst exhibits excellent performance at a lower temperature of 550°C and a long run time of 20 to 50 hours. This contributes to the efficient production of H-CNG with a high level of energy saving. The formed spent catalyst containing charcoal and carbon nanotubes can be used directly as a composite material, adsorbent, and other important applications without separation. In addition, the resulting carbon nanotubes are of high purity (more than 90%). On the other hand, MWCNTs have minimal structural defects and are optimal for use in the steel, cement, and electronics industries.

[00127] While the subject matter has been described in sufficient detail with reference to certain embodiments, other embodiments are possible. Thus, the spirit and scope of the disclosure cannot be limited to the description of the embodiments provided herein.

Claims (27)

1. A catalytic composition for producing gaseous hydrogen, containing: (a) nickel; (b) at least one of the following promoters: Cu, Zn; And (c) a carrier that is steamed biochar or an equilibrium liquid catalytic cracking spent material catalyst; moreover, the proportion of nickel is 6-19 wt.%, and the proportion of at least one promoter is 0.5 wt.% with respect to the carrier. 2. Composition according to claim. 1, in which the steamed biochar has a surface area of 700-950 m ² /g and a pore volume of 0.60-0.70 cm ³ /g. 3. The composition of claim. 1, in which the steamed biochar is obtained by heating the feedstock of the carrier, which is sawdust, rice straw, rice husk, sugar cane pomace, other agricultural waste, or combinations thereof. 4. A method for manufacturing a catalytic composition for producing gaseous hydrogen according to claim 1, containing: (a) contacting a nickel salt and a salt of at least one promoter to obtain a mixture; (b) impregnating the carrier with the mixture to form an impregnated catalyst material; And (c) calcining the impregnated catalyst material to obtain a catalyst composition. 5. The method according to claim 4, wherein the carrier is steamed biochar obtained by steaming raw materials, which are sawdust, rice straw, rice husks, sugar cane pomace, other agricultural waste, and combinations thereof, at a temperature of 700-900°C within 5-10 hours. 6. A method for producing gaseous hydrogen from a light hydrocarbon, containing: (a) adding the hydrogen gas catalyst composition of claim 1 to the reactor; (b) passing a light hydrocarbon over the catalyst bed at a temperature of 300-750°C and atmospheric pressure for 20-50 hours; And (c) obtaining a product stream containing hydrogen gas. 7. The process of claim 6 wherein the product stream is free of carbon monoxide and carbon dioxide. 8. The method according to p. 6, as a result of which 10-30% of gaseous hydrogen is obtained from the total content of light hydrocarbons. 9. A method for producing carbon nanotubes from a light hydrocarbon, containing: (a) adding the hydrogen gas catalyst composition of claim 1 to the reactor; (b) passing a light hydrocarbon over the catalyst bed at a temperature of 300-750°C and atmospheric pressure for 20-50 hours; And (c) obtaining a product stream containing hydrogen gas and a mixture; (d) processing the mixture to obtain carbon nanotubes. 10. The process of claim 9 wherein the product stream is free of carbon monoxide and carbon dioxide. 11. The method of claim 9 wherein the carbon nanotubes are 90-99% pure. 12. The method according to any one of paragraphs. 6-11, wherein the light hydrocarbon is methane, ethane, propane, butane, ethylene, acetylene, or combinations thereof. 13. The method according to any one of paragraphs. 6-12, wherein the reactor is a fluidized bed reactor, a moving bed reactor, a fixed bed reactor, or a rotating bed reactor.

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